Java 9 new features (#660)

* initial push for core-java-9 tutorials

* Fixed Maven build with experimental java 9 Maven compiler plug-in. Minor
code changes

* Running maven build and changes to some of tests.

* Fixed maven build and modifications ot some tests

* Removing unnecessary files

core-java-9/src/main/java/.gitignore

@@ -0,0 +1,13 @@
+*.class
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+
+# Packaged files #
+*.jar
+*.war
+*.ear

core-java-9/src/main/java/com/baeldung/java9/language/PrivateInterface.java

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+package com.baeldung.java9.language;
+
+public interface PrivateInterface {
+    
+    private static String staticPrivate() {
+        return "static private";
+    }
+    
+    private String instancePrivate() {
+        return "instance private";
+    }
+    
+    public default void check(){
+        String result = staticPrivate();
+        if (!result.equals("static private"))
+            throw new AssertionError("Incorrect result for static private interface method");
+        PrivateInterface pvt = new PrivateInterface() {
+        };
+        result = pvt.instancePrivate();
+        if (!result.equals("instance private"))
+            throw new AssertionError("Incorrect result for instance private interface method");
+    }
+}

core-java-9/src/main/java/com/baeldung/java9/process/ProcessUtils.java

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+package com.baeldung.java9.process;
+
+import java.io.File;
+import java.io.IOException;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.stream.Stream;
+
+
+public class ProcessUtils {
+
+    public static String getClassPath(){
+        String cp = System.getProperty("java.class.path");
+        System.out.println("ClassPath is "+cp);
+        return cp;
+    }
+
+    public static File getJavaCmd() throws IOException{
+        String javaHome = System.getProperty("java.home");
+        File javaCmd;
+        if(System.getProperty("os.name").startsWith("Win")){
+            javaCmd = new File(javaHome, "bin/java.exe");
+        }else{
+            javaCmd = new File(javaHome, "bin/java");
+        }
+        if(javaCmd.canExecute()){
+            return javaCmd;
+        }else{
+            throw new UnsupportedOperationException(javaCmd.getCanonicalPath() + " is not executable");
+        }
+    }
+
+    public static String getMainClass(){
+        return System.getProperty("sun.java.command");
+    }
+
+    public static String getSystemProperties(){
+        StringBuilder sb = new StringBuilder(); 
+        System.getProperties().forEach((s1, s2) -> sb.append(s1 +" - "+ s2) );
+        return sb.toString();
+    }
+}

core-java-9/src/main/java/com/baeldung/java9/process/ServiceMain.java

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+package com.baeldung.java9.process;
+
+import java.util.Optional;
+
+public class ServiceMain {
+
+    public static void main(String[] args) throws InterruptedException {
+        ProcessHandle thisProcess = ProcessHandle.current();
+        long pid = thisProcess.getPid();
+
+        
+        Optional<String[]> opArgs = Optional.ofNullable(args);
+        String procName = opArgs.map(str -> str.length > 0 ? str[0] : null).orElse(System.getProperty("sun.java.command"));
+
+        for (int i = 0; i < 10000; i++) {
+            System.out.println("Process " + procName + " with ID " + pid + " is running!");
+            Thread.sleep(10000);
+        }
+
+    }
+
+}